❤️ 3.6 - 3.6.1 - 3.6.1.1 Survival and response (A-level only) Flashcards
Plants and animals respond to changes in their external environment to …
… increase their chances of survival
Animals respond to changes in their internal environment to make sure that the conditions are always optimal for their …
… metabolism (all the chemical reactions that go on inside them).
What is a stimulus?
Any change in the internal or external environment.
Receptors detect …
stimuli.
They can be cells or proteins on cell surface membranes. There are lots of different types of receptors that detect different stimuli.
Effectors produce a …
… response.
Effectors are cells that bring about a response to a stimulus to produce an effect. Effectors include muscle cells and cells found in glands, e.g. the pancreas.
Receptors are …….. to one type of stimulus.
specific
What do receptors communicate with effects via?
The nervous system or the hormonal system or both.
What does the nervous system send information as?
Electrical impulses.
The nervous system is made up of a complex network of cells called what?
neurones.
What are the 3 main types of neurones?
Sensory neurones, motor neurones and relay neurones.
What do sensory neurones transmit electrical impulses from and to?
From receptors to the central nervous system (CNS) - the brain and spinal cord.
What do motor neurones transmit electrical impulses from and to?
From the central nervous system (CNS) to effectors.
What do relay neurones transmit electrical impulses between?
Sensory neurons and motor neurones.
What are electrical impulses also called?
Nerve impulses or action potentials.
How does a stimulus make its way to an effector?
Stimulus – Receptors – sensory neurone– CNS –motor neurone– Effectors – Response.
When a stimulus is detected by receptor cells an electrical impulse is then sent along what type of neurone?
Sensory neurone.
When an electrical impulse reaches the end of a neurone, chemicals called neurotransmitters take the information across to the next neurone, which then sends what?
An electrical impulse.
The CNS (the coordinator) processes the information and sends impulses along what type of neurones to an effector?
Motor neurones.
What are the two different systems in which the nervous system is split into?
1) The central nervous system (CNS) - made up of the brain and the spinal cord.
2)The peripheral nervous system - made up of the neurones that connect the CNS to the rest of the body.
What are the two different systems in which the peripheral nervous system is split into?
1) The somatic nervous system - controls conscious activities, e.g. running and playing video games.
2) The autonomic nervous system - controls unconscious activities, e.g. digestion.
What are the two opposite effects in which the autonomic nervous system has on the body?
1) The sympathetic nervous system - gets the body ready for action (fight or flight system).
2) The parasympathetic nervous system - calms the body down (rest and digest system).
What are reflexes?
The are rapid, automatic responses to stimuli.
A reflex is …
… where the body responds to a stimulus without making a conscious decision to respond.
Why are reflexes rapid?
Because you don’t have to spend time deciding how to respond, the information travels really fast from receptors to effectors.
Because they are rapid, simple reflexes help to what?
Protect the body.
What is a reflex arc?
The pathway of neurones linking receptors to effectors in a reflex.
A simple reflex arc involving the 3 neurones (sensory, relay and motor) =
The hand-withdrawal response to heat.
1) Thermoreceptors in the skin detect the heat stimulus.
2) The SN carries impulses to the RN.
3) The RN connects to the MN.
4) The MN sends impulses to the effector (your biceps muscle).
5) Your muscle contracts to withdraw your hand and stop it being damaged.
If there is a relay neurone involved in the simple reflex arc, what is it possible to do?
Override the reflex, e.g. in the hand-withdrawal response to heat example, your brain could tell your hand to withstand the heat.
What are three words you could use to describe nervous system communication?
Localised, short-lived and rapid.
How is the nervous response localised?
When an electrical impulse reaches the end of a neurone, neurotransmitters are secreted directly onto target cells (e.g. muscle cells).
How is the nervous response short-lived?
Neurotransmitters are quickly removed once they have done their job.
How is the nervous response rapid?
Electrical impulses are really fast.
Plants sense the direction of light and grow towards it to maximise light absorption for …
… photosynthesis.
Plants sense gravity, so the roots and shoots grow in the right …
… direction.
Climbing plants have a sense of touch, so they can find things to climb up and reach the …
… sunlight.
Tropism defintion.
A tropism is the response of a plant to a directional stimulus (a stimulus coming from a particular direction).
How do plants respond to stimuli?
By regulating their growth.
A positive tropism is growth … the stimulus.
towards
A negative tropism is growth … from the stimulus.
away
Phototropism defintion.
The growth of a plant in response to light.
Are shoots positively phototropic and grow towards light?
Yes.
Are roots negatively phototropic and grow away from light?
Yes.
Gravitropism defintion.
The growth of a plant in response to gravity.
Are shoots negatively gravitropic and grow upwards?
Yes.
Are roots positively gravitropic and grow downwards?
Yes.
How do plants respond to directional stimuli?
By using specific growth factors.
What are growth factors in plants?
Hormone-like chemicals that speed up or slow down plant growth.
What are growth factors in plants produced in?
The growing regions of the plant (e.g. shoot tips, leaves) and they more to where they are needed in the other parts of the plant.
What is the name of a growth factor in plants, beginning with A?
Auxins.
What do auxins stimulate and how?
They stimulate the growth of shoots by cell elongation (where the cell walls become loose and stretchy, so the cells get longer).
What can high concentrations of auxins do?
Inhibit growth in roots of plants.
What is the name of an important auxin?
Indoleacetic Acid (IAA).
Where is IAA produced?
In the tips of shoots in flowering plants.
What is IAA moved around the plant to control? How does it move?
Tropisms - it moves by diffusion and active transport over short distances, and via the phloem over long distances.
What does different parts of the plant having different concentrations of IAA mean for the plant?
That there is an uneven distribution of IAA which means that there is uneven growth of the plant.
In phototropism, IAA moves to the more shaded parts of the shoots and roots, so there is uneven growth. True or false?
True.
In the shoot, IAA concentration increases on the shaded side - cells elongate and the shoot bends towards the …
… light.
In the root, IAA concentration increases on the shaded side - growth is inhibited so the root bends away from the …
… light.
In gravitropism, IAA moves to the underside of shoots and roots, so there is uneven growth. True or false?
True.
In the shoot, IAA concentration increases on the lower side - cells elongate so the shoot grows …
… upwards.
In the root, IAA concentration increases on the lower side - growth is inhibited so the root grows …
… downwards.
What do simple responses keep simple organisms in?
A favourable environment.
What are the two types of responses simple organisms can carry out to keep themselves in their favourable environment?
Tactic responses (taxes) or either kinetic responses (kinesis).
What are tactic responses (taxes)?
The organisms move towards or away from a directional stimulus, e.g. light.
What are kinetic responses (kinesis)?
The organisms movement is affected by a non-directional stimulus, e.g. humidity.
What are tactic responses called?
Taxes.
What are kinetic responses called?
Kinesis.
